


Entwined Lives

by vinndetta



Category: Undertale (Video Game)
Genre: M/M, Male Frisk, No More Resets, Post-Pacifist Route, Sans is curious, Smut, one day, perhaps, soon
Language: English
Status: In-Progress
Published: 2016-02-07
Updated: 2016-05-15
Packaged: 2018-05-18 22:35:03
Rating: Mature
Warnings: Underage
Chapters: 2
Words: 3,201
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5945827
Author URL: https://archiveofourown.org/users/vinndetta/pseuds/vinndetta
Summary: <blockquote class="userstuff">
              <p>"What's in your pants?"</p><p>"Determination!"</p><p>Sans isn't too sure, and maybe, just maybe, trying to find out the truth would be just worth all his trouble.</p>
            </blockquote>





	1. Chapter 1

"Hey, Frisk, right?"

"... yes?"

"Are you a boy or a girl?"

"... no."

"...What's in your pants?"

"Determination~!"

\-------

Every single day, Sans found something to worry about: whether it was Papyrus getting himself into unexplainable positions, whether another case of food poisoning would occur, or if the world would explode one day.

But lately what's been on his mind was a certain person. A human dropped down from the outside into the Underground, who broke the barrier between both worlds, who became friends with even the most violent of people and monsters, whose hair flowed in the wind, whose face scrunched up a lot in deep thoughts, who stayed with the monsters instead of staying with their kind.

Sans didn't understand why he was so obsessed with Frisk. They were just a person who seemed to be always silently watching everyone around them. Sure, they had opened up more and more each year that passed by, but Sans realized he didn't really know who Frisk was. Sans didn't even know what gender this person was. Their voice wasn't particularly high-pitched or low-pitched, and their body figure would not particularly connected to one gender or another. It seemed like gender wasn't in Frisk's vocabulary.

Sans shook his head and turned onto his side. His bed covers were completely off and he stared at the bare plain ceiling. Why was he even so obsessed with them? Frisk is of a different species, different from him in every way possible, but yet, there was something interesting about them, since the moment they stared each other in the eyes when Frisk exited from the Ruins.

\--------

_Sans hid behind the trees, in a clearing near the exit of the Ruins. He was hiding from his brother. Again. Papyrus was too much at times. He was much too obsessed with humans, though he's never seen one. Sans couldn't particularly understand it. He's seen the dead body of one (or two... or... well, more), and these humans weren't particularly interesting._

_That didn't matter. He was watching the doors of the Ruins. One of his friends with a love of puns like him made him swear a promise. If a human ever walked outside of the Ruins, he'd promise to protect them as best as he could. And so it was. A human's never exited since he's promised Toriel, but who knows? Maybe today's a special day._

_Sans suddenly heard a cough behind him. He perked up, eyes glowing in... what was it? Fear? Alarm? Excitement? Confusion? The blue circle around his eyes glowed with almost a dark passion, and he slowly peeked from behind the trees in sudden fascination at the figure he saw on the road._

_It was a human. The first human he's seen... alive... And this one seemed quite off. The human strolled through as if there was no worry in the world. Sans knew that if Papyrus found this human, some very interesting events would occur. There was so much to worry about if he was a human going through the Underworld. Sans couldn't quite get what this human was thinking._

_Slowly, he came from behind the trees and followed this interesting human. Was this a female or a male? This one had short-ish hair with a figure that made it impossible to see gender from a distance. Evidently, it became obvious that he was noticed when Sans realized that the human was pausing a bit, probably hearing Sans walking behind them. Instead of turning around, the human kept going down the road. Sans found this particular, and interesting. Fearless, and worryless. The exact opposite of what he was. They walked with a graceful step in a confident pose, while Sans nearly stomped with self-doubt. Sans snuck a small bag up their sleeve, just in case._

_The human reached the bridge, and Sans knew that Papyrus would be around there to look for humans. Sans cleared his throat, and appeared behind the human, saying in a dark voice:_

_"don't you know how to greet a new pal...? turn around and shake my hand."_

_The human suddenly stopped and stood there. Before Sans realized it, he was breathing in their scent. They smelled strangely of... cake. And cinnammon. Not a lot of people eat cinnamon cake. Hm... was that also the small of... butterscotch?_

_Sans cleared his throat yet again. The human then turned around, their hair whipping behind them. The human had pretty eyes the color of, ironically, cinnamon, and their slight smile reminded Sans of a person who was quiet, soft, and watchful. The human met the sketeton's eyes, and they looked up, not with surprise or horror of a walking skeleton wearing clothes, but in pure wonder. Sans stared slightly down at the human, and the human continued to stare up in curious fascination. Sans would probably go on to talk and introduce himself, but he seemed frozen in place, staring into the deep abyss of the human's eyes._

_"the name's sans. sans the... skeleton, obviously. sans the skeleton." Sans found that his voice somehow wasn't working and he was stumbling over his words._

_The human closed their eyes and let out a small giggle. The human smiled genuinely and waved at the gaping skeleton. The skeleton, realizing his awkwardness, reached out his hand._

_"go on, shake my hand."_

_The human tilted its head and then took his hand, which proceeded to make a loud fart noise. The human, realizing that Sans had put a whoopee cushion in his hand, giggled more than before. Sans was taken aback: the jokes and pranks never seem to truly amuse his brother, Papyrus._

_"you find that funny?"_

_The human nodded and closed their eyes in a genuine happiness. Sans breathed in the sweet smell of cinnamon and, for the first time in a long time, he smiled._

\--------

Sans closed his eyes. Being with Frisk was made him feel happier than he's felt in a long time. Since the barrier broke and monsters along with humans lived in harmony, Sans felt a purpose in life.

Of all people, Frisk, almost emotionless and silent, had saved the Underground and unite both worlds. Just another human who was 'supposed' to have met the same fate that other humans met. But instead, Frisk survived, willing to survive. Sans shook his head. He would never understand this obsession, would he?

But seriously, what gender is this Frisk?

\---------

Sans decided to make a list of plans on figuring out this pressing question.

\---------

PLAN A: just ask Frisk directly.

"hey, Frisk, are you a boy or a girl?"

"..."

PLAN A: FAIL

\---------

PLAN B: ask anyone else?

"I'm sorry, I don't know... though the question is quite... sans-sational..."

"I dunno. If asking doesn't work, then why would any of us know?"

"Humph. You're still obsessed over the human?"

"Please, everyone would know if I knew, dear Sansy!"

"... I'm afraid the great Papyrus doesn't know everything, sorry, Sans."

Sans hopes the other 24 letters of the alphabet work out, or else he’s going to have to go to his last resort.

\--------

Sans cursed under his breath as he stood in front of Frisk’s room. It’s been a week since Plan A was started, and Sans still hasn’t figured anything out using his original plans.

Sans still doesn’t understand his somehow obsession with this human. Standing in the dark, here, a feeling washes over Sans: maybe he's walking into something he shouldn’t. But a pull brings Sans back over and over again to Frisk. This same pull brought Sans in front of Frisk’s room, waiting for the right time to open that door.

He cracked open the door, and an eerie feeling washed over Sans, as if the sin he was about to commit was crawling on his back, waiting to haunt him. He went ahead anyway, and tip-toed inside. The room was a pale color of purple - or maybe that's what it seemed like in the dark - and pictures of Frisk and their friends were everywhere. At the head of the bed was a picture of Sans and Frisk, having their first date.

Sans blinked, standing a few feet from the door. In fact, he had almost forgotten about that 'date' they had.

\--------

_It had been years since Frisk went to be the official ambassador between the humans and the monsters. None of the monsters had seen them in a long time. Frisk kept in contact by cell phone with all of their monster friends, but he was always busy, keeping the peace between monsters and humans._

_And if Sans had tibia honest, Sans kind of missed the human. Sans chuckled in amusement about his own joke._

_"Hm? What's so funny?"_

_Sans looked up, and found Papyrus looking at him weirdly. Sans was brought back to reality. He was in a 'car' driven by Toriel, and they were going... where again? Huh._

_"tibia honest, i forgot what i was thinking, but that happens a skele-ton of times anyway. i'm sure it was humer-us in any case."_

_"SANSSSSSSSSSSSSSSSSS!" The enraged cry came from Papyrus, while Toriel started laughing instead._

_"I'm sure your puns will entertain your date!" Toriel hummed._

_Sans had a confused look on his face for a minute, before realizing that he was in this 'car' for a reason: he was being driven to a blind-date his friends had set up._

_Sans internally groaned. These dates never end up well._

_..._

_Sans sat at a table in Grillby's new place on the Surface. Almost all the monsters had head up onto the surface already. There were a few stubborn few that stayed behind, but Sans knew that they would eventually come out._

_A shadow stood over Sans, who looked up to see Grillby in a white apron and striped clothes underneath._

_"Going all professional since you came to the surface, eh, Grillby?" Sans quipped, raising his nonexistant eyebrow. Grillby said no further words, but seemed to have an intimidating stare that was directed at Sans' eyes._

_"too much? anyway, i'll have a burg."_

_"Your date's not even here yet; have some manners, you comedian." Sans looked up at Grillby in a mixture of surprise, excitement, and snarkiness. Sans hadn't heard Grillby talk in a long time; his dark, deep voice tickling Sans' yet again nonexistant ears. Grillby hadn't talked much since Asgore started taking human souls, which made Grillby almost irritated with Asgore's idiotic decisions._

_"sorry, sorry, man!" Sans chuckled and waved him off. "since you know of my date and such, tell me when the person arrives, yes?" Grillby seemed to roll his eyes (Sans has known him for a long time, he knows when Grillby would do such a thing)._

_"Of course, my liege." Grillby quipped, imitating Sans while reciting the line mockingly. Sans humphed, knowing that the two came up with the line whenever someone said something incredibly stupid or annoying. "Unfortunately, I am involved in this stupid game your friends decided to play."_

_"wait, so you know who it is?" Sans said suddenly, once what he said finally processed. Grillby started walking away, not answering the question posed to him at all. Sans fumed internally, stopping himself from yelling at him when he knew he was in a public place with humans. He didn't need to get humans thinking he was some sort of weirdo, not with all of Frisk's work._

_Frisk! Of course! Sans facepalmed, checking his phone. If all the friends knew, then they would know, right? Frisk was always more open with Sans than anyone else, even Papyrus. Papyrus didn't normally have secrets to keep, but when he did, like now, he kept them well and hidden._

_* sans: hey kid. i was thinking, everyone sent me on a blind date. do you know about it? *_

_Sans closed his phone and looked up to see Grillby again, bringing him water while he was waiting. Grillby, no matter how much Sans pestered, would not tell Sans anything, yet alone open his mouth. He simply put the water on the table and walked away without a word._

_The phone in Sans' pants vibrated and he fumbled, getting the phone out with a frenzy. He opened the phone, and read the message that Frisk sent him._

_* frisk (a.k.a. kid): I dunno, Sans. I mean, well... I'm a little busy too dealing with my own. *_

_Dealing with your own? Sans thought of the meaning of this. Some people said 'my own' when they referred to their children. Did Frisk have children? Somehow, when this thought came to his mind, his soul clenched and he winced. Heh, of course not, that's proposterous. What, how old is Frisk now? 18? Nah, can't be. Humans don't get married until their 20s or 30s usually, or at least that's what Sans pondered._

_There was a tap on his shoulder and Sans turned around to see Grillby. There was a figure behind him, his date? Maybe not, maybe so?_

_"hey grillby! you have my date?" Grillby stepped aside to reveal a human who had wavy brown hair that complemented their shoulders nicely. Their brown eyes settled onto Sans and their mouth practically hit the floor._

_"Sans?" they exclaimed, with phone in hand._

_"frisk?"_

_..._

_Grillby led Frisk to their seat across from Sans, while the two of them simply gaped at each other._

_Frisk looked away first, to glare at Grillby. "When you said my date was a nice guy that really likes me, I thought you were joking, Grillby! Well, yeah, he's nice and hot, but seriously?"_

_Sans blinked at the exchange, eyes directed at Frisk with confusion. Frisk looked at Sans, the cheeks lightly flushed, and coughed. "Oh, well, this is awkward... ahaha..."_

_"Cute~!" a sudden voice chirped._

_"We're supposed to be quiet, Alphys!"_

_"S-sorry, Undyne..."_

_Sans turned around quickly. A few figures got up from behind a few tables, revealing the bunch of friends that got Frisk and Sans into this mess. Sans glared at the bunch of idiots that he called friends. Cameras in their hands, they snorted and chuckled at the promising situation the two friends found themselves in._

\--------

Sans coughed, flushing a little at the embarrassing memory. Blind dates set up by his friends were always disasters for him. Just the thought of the date with Frisk made his bones almost shiver with a chilling feeling. The room seemed to be ever dark and sinister, as Sans looked around warily for a sign of comfort.

A sudden creak on the bed made Sans freeze. The dark figure moved on the bed, turning on its side. Sans breathed out with relief. It was only Frisk rolling around on the bed.

Frisk was now facing away from Sans, towards the opposite wall. Sans gulped. Perhaps this wasn't a great idea. Sans scolded himself internally for not thinking this plan over.

But it was already too late. He had gone this far already in any case.


	2. Chapter 2

Sans found himself in quite a predicament. Was he really willing to go this far to see what Frisk was? Why was he so obsessed with Frisk anyway?

Sans couldn't find any answer to his own questions. Sans looked around, making sure that there wasn't anything strange in his surrounding area. Once he was sure that he was alone in the room with Frisk - which made his heart skip a beat - he let out a breath that he didn't even know he was holding in the first place.

Sans slowly crept towards Frisk. Sans, on his hands and knees, crawled across the room to the opposite wall. It was still dark, and Sans wasn't even sure if Frisk was a heavy sleeper or not. 

Sans felt an instant pang of regret. This might ruin their friendship if he was ever found out. What if Frisk woke up and screamed? 

Maybe this wasn't such a good idea after all. Sans felt his sins crawling on his back, and he decided to keep on going. 

He was determined to find out.

Sans got on his knees to peep above Frisk's bed. He could see Frisk's face, with no emotion whatsoever. Frisk was breathing slowly, and Sans felt reassured that at least Frisk wasn't awake.

Sans, with a sudden burst of determination, slowly pulled up the covers and crept underneath them. Frisk's body heat kept the bed warm and Sans almost wanted to sleep here and bathe in the warmness. Frisk was just so warm, and Sans almost wanted to lie here with Frisk.

Sans had a mission, he thought to himself. He had to do this.

Sans slowly reached out with a shaking hand to Frisk. He found that Frisk's belly was extremely soft. His hands crept down to find Frisk's shorts. These shorts were made of cotton; they were soft just like Frisk's skin.

Sans' breath hitched as he slowly pulled down Frisk's shorts. 

No, no, no, this isn't right. Why are you doing this, Sans asked himself in his own thoughts. There was no answer, and Sans pulled his hands back.

Frisk was shifting.

Fuck.

\-----

Sans laid there in horror as his face was directly in front of Frisk's. 

Sans' inner voice screamed in worry. Frisk was going to find out. Frisk was going to find out what a terrible monster he was. Frisk was going to find out that he would go to terrible lengths to find out what Frisk was. Frisk would never ever forgive him for doing such horrible things to him.

Frisk was going to hate him forever.

Sans' thoughts dissipated as Frisk stopped shifting.

That was a close call. Sans reached out again - despite his inner voice screaming not to - and felt his hand touch Frisk's hip.

Sans reached down and found that he was touching a very hard piece of flesh.

"My, my, Sansy. Couldn't even wait for me to even be awake."

Fuck.

\-----

"This is an interesting predicament you're in right now." 

Sans looked up into Frisk's eyes, and proceeded to close his eyes shut. He knew this was going to happen. Why didn't he stop when he had a chance?

Frisk tilted their head in confusion. They lifts Sans' head to force him to face Frisk.

"Sans, look at me. Sans, please, it's alright."

There was no response, and Frisk sighs.

"You've been trying to figure it out. I don't care much for pronouns or who I'm supposed to be."

Sans opens his eyes.

"It was kind of hot though." Frisk hums. "Just trying to figure out who I am... by what, trying to see my sexual organs?"

Sans buried his head in Frisk's neck.

"sorry... kid. i just got carried away... i should leave..."

Sans tried to get up and leave the area. He knew that this was going to be terrible and he knew he wouldn't be able to look into Frisk's eyes for a very long time.

There was a sudden change in the atmosphere, and before Sans knew it, he was on his back with Frisk above him. Sans' heart skipped a beat and his cheeks flushed a florescent blue. Frisk noticed this change in him immediately and winked at Sans flirtatiously.

"Carried away, huh? Don't try to leave me after you've gotten me all flustered."

**Author's Note:**

> So is it obvious yet? The sins of Undertale have gotten to me, hehe.
> 
> sin


End file.
